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Python program to extract key-value pairs with substring in a dictionary

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  • Difficulty Level : Basic
  • Last Updated : 01 Oct, 2020

Given a dictionary list, extract all the dictionaries which have substring present in particular key.

Input : [{“Gfg” : “4”, “best” : “1”}, {“Gfg” : “good CS content”, “best” : “10”}], K = “Gfg”, sub_str = “CS” 
Output : [{‘Gfg’: ‘good CS content’, ‘best’: ’10’}] 
Explanation : “Gfg” has “CS” as substring value.

Input : [{“Gfg” : “4”, “best” : “1”}, {“Gfg” : “good content”, “best” : “10”}], K = “Gfg”, sub_str = “CS” 
Output : [] 
Explanation : No dictionary with “CS” as substring to “Gfg” key. 

Method #1 : Using list comprehension

This is one of the ways in which this task can be performed. In this, we iterate for all the dictionaries and check for key’s value substring presence using in operator.

Python3




# Python3 code to demonstrate working of
# Dictionaries with Substring values
# Using list comprehension
  
# initializing lists
test_list = [{"Gfg": "4", "best": "1"},
             {"Gfg": "good for CS", "best": "8"},
             {"Gfg": "good CS content", "best": "10"}]
  
# printing original list
print("The original list : " + str(test_list))
  
# initializing K key
K = "Gfg"
  
# initializing target value
sub_str = "CS"
  
# list comprehension to extract values with
# substring values using in operator
res = [val for val in test_list if sub_str in val[K]]
  
# printing result
print("Dictionaries with particular substring values : " + str(res))

Output:

The original list : [{‘Gfg’: ‘4’, ‘best’: ‘1’}, {‘Gfg’: ‘good for CS’, ‘best’: ‘8’}, {‘Gfg’: ‘good CS content’, ‘best’: ’10’}]
Dictionaries with particular substring values : [{‘Gfg’: ‘good for CS’, ‘best’: ‘8’}, {‘Gfg’: ‘good CS content’, ‘best’: ’10’}]

Method #2 :  Using map() + in operator

This is yet another way in which this task can be performed. In this, we extract all the values with required substring using map() + lambda function. The in operator is used to check for substring inside the key’s value.

Python3




# Python3 code to demonstrate working of
# Dictionaries with Substring values
# Using map() + in operator
  
# initializing lists
test_list = [{"Gfg": "4", "best": "1"},
             {"Gfg": "good for CS", "best": "8"},
             {"Gfg": "good CS content", "best": "10"}]
  
# printing original list
print("The original list : " + str(test_list))
  
# initializing K key
K = "Gfg"
  
# initializing target value
val = "CS"
  
# map() used to perform filtering
res = list(map(lambda sub: val in sub[K], test_list))
res = [test_list[idx] for idx, ele in enumerate(res) if res[idx]]
  
# printing result
print("Dictionaries with particular substring values : " + str(res))

Output:

The original list : [{‘Gfg’: ‘4’, ‘best’: ‘1’}, {‘Gfg’: ‘good for CS’, ‘best’: ‘8’}, {‘Gfg’: ‘good CS content’, ‘best’: ’10’}]
Dictionaries with particular substring values : [{‘Gfg’: ‘good for CS’, ‘best’: ‘8’}, {‘Gfg’: ‘good CS content’, ‘best’: ’10’}]


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